The objectives of this study are to review and summarize published information on the use, effectiveness, and adverse effects of intravenous immunoglobulin (IVIG) in patients with polymyositis (PM) or dermatomyositis (DM) and to search MEDLINE and CNKI (Chinese) databases from 1985 to 2011 to retrieve clinical research articles concerning IVIG in adult patients with PM/DM. Of the 14 articles selected, two were randomized controlled trials, nine prospective open studies, and three retrospective studies with a total of 308 adult patients. IVIG has been used successfully in the treatment of PM/DM. The standard dose is 2 g/kg, given in two to five individual daily doses. The course of IVIG treatment is usually 3 similar to 6 months. IVIG therapy seemed rarely employed as first-line therapy in PM/DM. In a double-blind study conducted in patients with refractory DM, IVIG combined with corticosteroid significantly improved muscle strength and decreased serum creatine kinase level, compared with placebo. The beneficial effect of IVIG in refractory, flare-up, rapidly progressive, or severe PM/DM has been documented in many open-label trials. IVIG was shown to be effective in most of PM/DM patients with lung involvement and esophageal involvement. In some patients, IVIG can lower the corticosteroid dose required for maintenance, demonstrating the most effective steroid-sparing effect. Adverse effects were generally tolerable. IVIG is effective in the treatment of adult patients with PM/DM and appears to be relatively well tolerated and safe. IVIG may be a good choice especially in patients with refractory, flare-up, rapidly progressive, or severe PM/DM, and can be tried in patients with a contraindication for corticosteroid.